Qt Quick - design philosophy

I'm just starting with Qt Quick. So far, there are many impressive things but I was hoping someone would explain the design philosophy to me with respect to the look and feel of "widgets". Let's start with the humble button. It doesn't exist in QML. Instead it could be composed of a Rectangle, Text and MouseArea. Seems to me that this will lead to each application having its unique appearance. Since the first Apple Mac came out, we have known about the power of a consistent look and feel across all applications on a given platform. Within the design philosophy of Qt Quick, how will this be achieve this?

Qt Components is in an, let's say, alpha stage. If you get interested, in the repository pointed by danilocesar you'll find in the master branch a widget set for MeeGo (in progress). Also, check the branch mx, where you can see a widget set created in QML with the look and feel of the "MX toolkit":http://www.ohloh.net/p/mx-toolkit.